DVD-audio disks can sound slightly better than CD's, but not because of higher resolution.... its all about mastering and dynamic range. Most CD's are (as we know) dynamically compressed to sound as loud as possible, while DVD-audio releases may be less compressed. I have a few DVD-audio discs, and all of them are mastered with less compression than the CD version.

But - if you really want great sound - look for CD releases from the early 80's. That when they still had some dynamic range!

That's pretty ironic when you consider that one of the original selling points of CDs was their potential for a higher dynamic range over tapes and vinyl.

I've thought of another one I own... the 30th Anniversary Fly Like An Eagle by the Steve Miller Band includes a 5.1 channel version of the album. Albeit not really "closer to [the] vinyl recordings."
The DVD also includes a great live show with, of all things, a guest harp player. And I don't mean Norton Buffalo (RIP), I mean a real harp player. The stringed kind.

__________________
It is error only, and not truth, that shrinks from enquiry. - Thomas Paine

What about the audio on Blu-Ray discs? If you had Dolby TrueHD, would that work for testing 2 speakers alone? I have the impression from the descriptions on Blu-Ray discs that Dolby TrueHD was intended for a 5.1 speaker arrangement.